Ambient-pressure bulk superconductivity deep in the magnetic state of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$

Specific heat, magnetic susceptibility, and electrical transport measurements were performed at ambient pressure on high quality single-crystal specimens of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$ down to ultralow temperatures. We report signatures of an anomaly observed in all measured quantities consistent with a bulk thermodynamic phase transition to a superconducting state at $T_c=110\mathrm{mK}$. Occurring far below the onset of antiferromagnetism at $T_N=3.8\mathrm{K}$, this transition appears to involve a significant portion of the available low-temperature density of electronic states, exhibiting an entropy change in line with that found in other members of the 115 family of superconductors tuned away from quantum criticality.

Figure 1

(Color online) Specific heat of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$ with lattice contribution $C_{\mathit{latt}}$ subtracted (see text). Inset shows a zoom of low-temperature data and fit (solid line) composed of individual electronic plus magnetic ($C_e+C_m$, dashed line) and nuclear ($C_n$, dotted line) contributions as explained in the text.

Figure 2

(Color online) Signature of bulk ambient-pressure superconducting transition in $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$, extracted from the total specific heat via (a) a subtraction of the nuclear Schottky contribution $C_n$ as obtained from fits to the data (see text) for various magnetic fields and (b) a subtraction of the normal state $(H>H_{c2})$ specific heat $C\left(H\right)$ from the total zero-field specific heat $C\left(0\right)$.

Figure 3

Comparison of extracted specific heat transition (solid circles) [where $\Delta C=C\left(0\right)-C\left(120\mathrm{mT}\right)$ and $\gamma =56\mathrm{mJ}∕\mathrm{mol}{\mathrm{K}}^2$], and the diamagnetic response of the same $55\mathrm{mg}$ single-crystal specimen of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$ (open circles), showing the bulk full-volume nature of the ambient-pressure superconducting transition at $T_c=110\mathrm{mK}$. The superconducting transition in a similar sized single-crystal sample of $\mathrm{Rh}{\mathrm{In}}_3$ is also shown (triangles) for comparison.

Figure 4

(Color online) Low temperature resistivity of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_5$ in zero and applied magnetic fields. Dashed lines are linear fits to zero-field data below the kink associated with the onset (indicated by arrow) of the superconducting transition at $T_c$, showing a slight dependence on excitation current. The solid line is a quadratic fit to zero-field data above the kink.